The present invention relates generally to a vibratory plow which is adapted to lay cable, flexible pipe, and the like underground in the cut made by a blade wherein the blade is vibrated to reduce the force required to pull the blade through the ground. More particularly, the present invention relates to a vibratory plow assembly which provides for improved vibratory plowing.
Vibratory cable plows have been used for several years to lay cable, flexible pipe, and the like underground. The cable or pipe may be either pulled through the cut of the plow blade or a cable chute may be provided on the trailing edge of the plow blade which guides the cable or pipe into the ground from a drum mounted on the tractor or other vehicle. Various types of vibrators have been mounted on the plow blade, or the vibrator and blade have been suspended together on a resilient frame assembly to generate either vertical or orbital motion in the plow blade. Examples of such prior art vibratory plows are disclosed in U.S. Pat. Nos. 4,040,261, 3,618,237 and 3,363,423, all assigned to the assignee of the present invention.
A preferred frame assembly of prior art vibratory plows, as shown in the above-referenced patents, includes two pairs of parallel side links which are resiliently supported by torsional bearing connections to forward and rearward frame members comprising generally vertical stanchions or columns. The plow blade and vibrator are supported by the rearward frame member. The vibrator generates substantially vertical vibrations in the plow blade when the vehicle is stationary and orbital vibration in the blade as the blade is pulled through the ground.
The torsional bearing connections between the side links and frame members provide resiliency for the plow blade assembly, however, because of their stiffness, the entire plow assembly is not easily raised for transport. Further, since cable plow assemblies are large and heavy apparatus, it is very difficult to provide a lift arrangement that operates simply for raising the plow frame adequately for transport. For example, it is desirable to have a high angle of blade departure when loading a vibratory plow for transporting it to different locations such that the plow can be loaded and unloaded using a standard truck loading ramp without removing the blade. It is also desirable that the overall length of the prime mover and the plow assembly be relatively short to minimize the space taken on the trailer or truck bed. However, known vibratory plow frame geometry limits the angle of blade departure and forces the blade rearwardly as the plow is raised for transport. Thus, there has been a need for a lift mechanism that provides a high angle of departure and prevents rearward movement of the plow blade so that the vibratory plow assembly can be loaded onto a trailer without removing the blade.
In prior vibratory plow constructions of the type described above, the plow blades are also heavy and difficult to mount. Typically, the mounting of a vibratory plow blade requires precisely aligning the mounting holes in the long, heavy blade with corresponding holes in a blade holder and then driving pins into place through the mounting holes. This is a very difficult procedure to perform, particularly if there is a need in the field to repair or replace the plow blade. Thus, there has been a need for a vibratory plow construction which simplifies the mounting of the heavy plow blade.
Vibratory plows have also been provided with gage wheels to provide support to the vibrator and plow blade as well as flexing against the substantial vertical shaking. An example of such a construction is shown in U.S. Pat. No. 3,390,533. If, however, the plow blade either follows or precedes the gage wheels, as shown in the just-mentioned prior art patent, the blade and cable burial depth will not remain constant. Thus, there has been a need for a vibratory plow construction which locates the plow blade below the area where the gage wheels contact the ground so that any upward or downward movement of the gage wheels because of uneven ground will be directly transmitted to the blade, thereby maintaining the plow blade and cable burial depth constant regardless of the contour of the ground surface.
Maneuverability of the cable plow assembly is also desirable since it is common for the plowing to take place next to buildings, fences, obstructions, or along roadsides. For regular plowing in normal conditions, the vibratory plow boom is positioned such that the plow will follow the prime mover. However, when plowing next to buildings and the like, the plow blade must be moved laterally relative to the prime mover. Thus, there continues to be a need for a vibratory plow arrangement that provides for maximum maneuverability and easy operation for offset plowing.
It has now been discovered that a vibratory plow assembly constructed in accordance with the teachings of the present invention provides improved vibratory plowing and avoids the disadvantages and limitations of the prior constructions, as hereinabove described.